1. Field of the Invention
The present invention relates to an image projection apparatus.
2. Description of the Related Art
Conventionally known is an image projection apparatus including image forming unit having a digital mirror device (DMD) being an image generating element for generating an image based on image data received from a personal computer or the like; and an irradiation unit for irradiating the image generating element with light from a light source. In such an image projection apparatus, an image is formed in the image forming unit, and the image formed by the image forming unit is imaged on a projection surface using a projecting optical unit (for example, Japanese Patent Application Laid-open No. 2008-134432).
Specifically, the light from the light source, traveling in parallel with the image generating surface of the DMD, is folded by an illuminating optical system such as a folding mirror toward the image generating surface, so that the image generating surface is irradiated with the light. On the image generating surface of the DMD, a plurality of movable micromirrors are arranged in a grid-like arrangement. The mirror surface of each of the micromirrors can be tilted by a given angle about a rotational axis so that two states of “ON” and “OFF” can be set. While a micromirror is “ON”, the micromirror reflects the light from the light source toward the projecting optical unit. When the micromirror is “OFF”, the micromirror reflects the light from the light source toward a light absorber provided inside of the apparatus. Therefore, by driving each of the mirrors independently, projection of light can be controlled for each pixel in image data so that the image can be generated. The image generated by the DMD passes through the projecting optical unit and imaged on the projection surface.
The applicant is currently developing an image projection apparatus in which the length of the image projection apparatus is reduced in a direction perpendicular to the plane of a projected image that is projected on the projection surface, by arranging components of the image projection apparatus in a direction perpendicular to an installation surface for the apparatus main unit, that is, a surface on which the apparatus main unit is installed, e.g., a table top, a wall surface, or a ceiling. When the projecting optical unit and the image forming unit are connected and arranged in the direction perpendicular to an installation surface of the apparatus main unit, and a heat releasing unit is to be provided to the image forming element and the image forming unit, the heat releasing unit needs to be arranged between a member facing the installation surface where the apparatus main unit is installed and the image forming unit, and the heat releasing unit needs to be kept away from the member facing the installation surface.
As a way for supporting the image forming unit and the projecting optical unit connected and arranged in the direction perpendicular to an installation surface while keeping the heat releasing unit for the image forming unit away from the member of the apparatus main unit facing the installation surface, the image forming unit and the projecting optical unit may be fixed on a surface facing both of the image forming unit and the projecting optical unit in a manner conventionally practiced. In other words, the image forming unit and the projecting optical unit may be fixed to a member including a surface perpendicular to the installation surface of the apparatus main unit. In such a configuration, the member including the surface perpendicular to the installation surface of the apparatus main unit is provided with supporting portions such as screw receptacles, for example, and the image forming unit and the projecting optical unit are fixed to the supporting portions. In this configuration, the weights of the image forming unit and the projecting optical unit are supported by the member including the surface perpendicular to the installation surface of the apparatus main unit.
Because a bending moment is applied by the weights of the image forming unit and the projecting optical unit to the supporting portions that are provided to the member including the surface perpendicular to the installation surface of the apparatus main unit, the member including the surface perpendicular to the installation surface of the apparatus main unit needs to have some strength. To increase the strength of the member including the surface perpendicular to the installation surface of the apparatus main unit, it is necessary to increase the thickness of the member including the surface perpendicular to the installation surface of the apparatus main unit, or to provide ribs to the member including the surface perpendicular to the installation surface of the apparatus main unit, for example. Therefore, a material cost for the member including the surface perpendicular to the installation surface of the apparatus main unit is increased; and therefore, the cost of the apparatus is increased disadvantageously.
Furthermore, if the image forming unit and the projecting optical unit are fixed to one of a plurality of members including the surface perpendicular to the installation surface of the apparatus main unit and surrounding the image forming unit and the projecting optical unit, the weight balance is lost and the image projection apparatus might become easier to fall down. By making the entire image projection apparatus heavy, the image projection apparatus could be prevented from falling due to the lost balance, but portability is reduced if the image projection apparatus is heavy.
The present invention is made in consideration of the above. There is a need to provide an image projection apparatus that does not require strength in a member including a surface perpendicular to an installation surface of the apparatus main unit when optical units such as an image forming unit and a projecting optical unit are arranged in a direction perpendicular to the installation surface.